A microlens array is a group of lenses arranged two-dimensionally and having a center to center spacing of less than about 2 mm. Microlens arrays have various uses as described in European Patent Application 0,426,441 A2, including: (1) to intensify luminance by focusing light through picture elements in non-luminant display devices such as liquid crystal display devices; (2) as a light pickup means such as a laser disc, compact disc, or optical magnetic disc; (3) as a focusing means for coupling a luminant device or a receptive device to an optical fiber; (4) as a focusing means or an image forming means for focusing incident light in a photoelectric converting zone so as to increase the sensitivity of a primary image sensor used in a solid state image device such as a charge coupled device (CCD) or facsimile machine; (5) as an image forming means for forming an image on a sensitive medium to be printed on by a liquid crystal printer or an LED printer; and (6) as a filter for treating photo-information.
Liquid crystal displays are comprised of a large number of pixels, i.e., picture elements, which are display units arranged regularly between two optically transparent substrates. Images formed in the image plane of a liquid crystal display can be projected onto a screen by shining light through the display toward a projection lens. Such projection systems commonly suffer from a low brightness level because much of the light is lost in the display and never reaches the projection lens. It is known that microlens arrays can be provided on a liquid crystal display to improve the brightness of the projected image.
U.S. Pat. No. 5,052,783 (Hamaria) discloses a projection type image display apparatus which sandwiches a liquid crystal display between a pair of microlens arrays. The microlenses in the arrays are positioned so that light rays entering through the center of a given lens in one array pass through the center of a pixel in the liquid crystal display and exit through the center of a microlens in the other array.